摘要:

In this paper, a generalised Villeneuve type linear array distribution is developed, which permits the direct synthesis of discrete array distributions for high efficiency sum patterns of arbitrary sidelobe level and envelope taper. With the Dolph–Chebyshev distribution as the parent space factor, and the correct perturbation of these space factor zeros, the excitation efficiency and beamwidths are kept as close to their optimum values as is possible under the given sidelobe ratio and envelope taper conditions. The method is the discrete analogue of the generalised Taylor n̅-distribution, used for continuous line source synthesis. Examples are given to illustrate the principal features of the distribution.

DOI:10.1049/ip-h-2.1989.0045

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The application of the concept of intrinsic modes to the theory of propagation in conical corrugated horns is developed. An intrinsic mode is an exact solution of source-free Maxwell equations which satisfies the boundary conditions to a prescribed order of accuracy as the flare angle α becomes small. There exists an infinite number of intrinsic modes for a given structure and each one corresponds with a fixed local normal mode at every cross-section, to which it approximates asymptotically as α → 0. An intrinsic mode is given by a Fourier-like spectral integral which is uniformly valid, including the regions where the corresponding local normal mode is evanescent or in transition from propagating to evanescent. This spectral integral can be generated from knowledge of onlyonelocal normal mode at each cross-section, and numerical calculations show that the intrinsic mode based on theHE11local normal mode is sufficient for many applications, including the calculation of crosspolar radiation.

DOI:10.1049/ip-h-2.1989.0046

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The distributions of the electric and magnetic fields and power of the classic rectangular waveguide twin-slab ferrite phase shifter, with one region magnetised along the positivey-direction and the other along the negativey-d irection, are re-examined in the paper. It indicates that this type of device may quite often be phenomenologically described by a nonreciprocal edge-mode effect, rather than, as is customary, in terms of circular variables. This model may be of value in the design of practical wideband devices. The presence of counter-rotating magnetic fields at the two open faces of the ferrite region is also of note. The use of unequal oppositely magnetised sections is a possibility that has not received any attention so far.

DOI:10.1049/ip-h-2.1989.0047

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The spectral domain analysis is applied to study the effects of dielectric cover on a circular microstrip patch antenna. Numerical examples indicate that the resonant frequency of the patch is decreased considerably while the bandwidth is varied slightly.

DOI:10.1049/ip-h-2.1989.0048

出版商:IEE    

年代:1989

数据来源: IET

摘要:

In this paper, the method of moments is utilised to investigate the radiation characteristics of the two-dimensional version of a short backfire antenna excited by an input TEM mode. The theoretical predictions of the far field patterns and the input VSWR are in very good agreement with measurements performed on an actual prototype designed for the X-band. The technique has the virtue that it can be readily applied to the more useful rectangular geometry.

DOI:10.1049/ip-h-2.1989.0049

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The moment method is used to solve the electric-, magnetic- and combined-field integral equation, to determine the current distribution on a semi-infinite, open-ended, circular waveguide. A standard triangle-function expansion is used to represent the exterior waveguide wall currents. The approximate nature of this current distribution is shown to lead to difficulties with the uniqueness of both the solutions associated with the electric- and magnetic-field integral equations. By examining the degree to which the boundary conditions are satisfied, the combined-field integral equation is shown to yield superior results.

DOI:10.1049/ip-h-2.1989.0050

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper demonstrates the method of generic curve series to obtain the profiles of dielectric antennas, with design conditions either for the specification of the aperture-amplitude distribution from a given source distribution, or for agreement with the Abbe sine condition. The method has already proved successful in the design of dual reflector antennas, and the extension to refractive media is shown to be straightforward. The method basically involves obtaining two equivalent expressions for a fundamental parameter from the usual optical equations and internal geometry of the lens, and obtaining agreement between them by a computational optimisation procedure using the series of curves. The parameter used in the paper is the internal segment of the ray within the lens. The method applies equally well to lenses with othera prioriconditions such as afocal linear magnification or off-axis bifocality.

DOI:10.1049/ip-h-2.1989.0051

出版商:IEE    

年代:1989

数据来源: IET